Sale on Muse clothing (T-shirts from £6, Hoodies from £15) and accessories.
Some of these are on sale for obvious reasons (not even us hardcore Muse fans would want to buy them) but a lot of these are good.
EDIT: It's worth noting that the T-Shirts from the Muse Shop (and gigs) are much nicer than those from HMV or PULP. These are the really soft ones with the Muse lables. The Muse.mu T-Shirts are not machine dryable, but IMO the better quality is worth it.